EFFICIENT PREDICTION OF RADIATION FROM PRINTED TRANSMISSION-LINE DISCONTINUITIES

Asymmetrical discontinuities in printed circuit traces may increase ra diated power significantly over the levels resulting from symmetrical traces such as parallel lines. In this paper, an efficient full-wave s pace domain Galerkin moment method is developed to compute the current distribution and the radiation associated with arbitrarily shaped mic rostrip (or printed transmission-line) discontinuities. Several techni ques are used to increase the efficiency of the method of moments (MoM ) algorithm so that a circuit of moderate electrical size can be analy zed in reasonable time. These include the utilization of 1) quasi-dyna mic and far-field approximations of the microstrip Green's functions w here applicable, and 2) the various symmetries in the problem formulat ion that facilitate an efficient fill-in of the moment matrix by avoid ing redundant calculations. The influence of asymmetrical currents on the radiation from some representative microstrip discontinuities is e xamined by appealing to the ideal structure extraction method (ISEM). Sample computed results are presented to show that the current distrib ution and the radiation associated with resonant size structures can b e significantly higher than the regulatory limits. The MoM algorithm i s validated by comparison of the computed current distribution and res onant frequencies of a microstrip transmission line with analytical re sults derived from quasi-TEM transmission-line theory.